But the snout is thought to have served another purpose. Experts believe that males and females rubbed their sensitive faces together in a prehistoric form of foreplay.

Writing in the journal Scientific Reports, the US authors describe how the sensitive skin may have proved crucial to the dinosaur’s mating success. “In courtship, tyrannosaurids might have rubbed their sensitive faces together as a vital part of pre-copulatory play,” they explain.

D horneri lived before T rex about 74m years ago and was three-quarters the size of its later cousin, with a body length of nine metres (29.5ft).

Unusually well preserved fossil skulls and skeletons of several of the creatures were found, including adults and juveniles.

It was the face of D horneri that yielded the most important information, opening a new window on tyrannosaur evolution and anatomy.

Scientists believe the dinosaur and other tyrannosaurs including T rex wore a mask of large, flat scales, with regions of tough and protective armour-like skin around the snout and jaws.

Strikingly, the hard surface of the snout was penetrated by numerous small nerve openings, or foramina.

These would have allowed hundreds of branches of the trigeminal nerve to reach the surface of the snout, turning the dinosaur’s face into a sensitive third “hand”.

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A similar arrangement is seen today in crocodiles and alligators, which have thousands of tiny sensitive bumps called integumentary sensory organs around their jaws. In 2011, scientists at the Yale Peabody Museum of Natural History in Connecticut reported that the animals rubbed these sensitive bumps on the face and body “profusely” before mating, and found the behaviours “frequently result in what appears to be overstimulation.”

Lead scientist Dr Thomas Carr, from Carthage College in Wisconsin, said: “Given that the foramina are identical in tyrannosaurs, [that] indicates that they had super-sensitive skin as well.”

The trigeminal nerve plays a special sensory role in many mammals, reptiles and birds, carrying sensory signals from whiskers and electrical receptors and enabling the pit viper to home in on infrared radiation from warm-blooded prey.

Crocodiles sense both touch and vibrations in water via the trigeminal nerve, while migrating birds may use it to detect magnetic fields.

Co-author Prof Jayc Sedlmayr, from Louisiana State University, said: “Our finding of a complex sensory web is especially interesting because it is derived from the trigeminal nerve which has an extraordinary evolutionary history of developing into wildly different ‘sixth senses’ in different vertebrates.”